11... a6b4 This tempting move is a mistake. Black should choose either 11...Ne7 or 11...Nh6. 12. e2f4 The refutation of Black's play. Robson needs a lot of praise to find all this over the board, in a rapid game, with the pressure of being caught in the opening. 12... g6f5  13. d1d6 13.Bxg7 is also possible, but it's so hard for a human to evaluate that I prefer the move played in the game. 13... f7f6 